Molten metal supply device and aluminum titanate ceramic member having improved non-wettability

ABSTRACT

An electromagnetic type molten metal supply device having superior accuracy in supplying molten metal. This device is comprised of a rotary vane that rotates in accordance with the movement of molten metal inside a molten metal transport conduit, and the amount of molten metal being transported can be measured by detecting the rotational frequency of the rotary vane.

CROSS-REFERENCE TO RELATED APPLICATION

This is a continuation of Application PCT/JP01/05571, filed Jun. 28, 2001, now abandoned.

BACK GROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a molten metal supply device that transports/supplies molten metallic aluminum and molten metallic sodium, for example. In addition, this invention relates to a technology for conferring and retaining the non-wettability of a ceramic member that comes into contact with a molten metal such as a molten aluminum alloy.

2. Description of the Related Art

For example, a linear induction electromagnetic pump that confers a thrust to a molten metal by means of the electromagnetic induction effect is used to transport molten metals such as molten metallic sodium in a fast breeder reactor or molten metallic aluminum in a casting facility.

In a molten metal supply device, in particular a molten metal supply device in a casting facility, it is important to supply a predetermined amount of molten metal to the cavity used for casting, in order to achieve casting accuracy.

A molten metal supply device having an electromagnetic pump supplies molten metal to a casting cavity or a cylinder by regulating the transfer velocity and the transfer time thereof, by means of various types of current controls, to regulate the current frequency supplied to the electromagnetic pump, the current density, the current supply time, etc.

However, since an electromagnetic pump confers a thrust to the molten metal, which is a fluid, it is difficult to accurately control the transfer volume thereof by means of current control.

Even when a discharge cylinder is provided for supplying a molten metal to the cavity, the molten metal supply accuracy of the electromagnetic pump ultimately becomes a problem. In addition, even if an orifice or valve is provided in the supply path to the cavity, the volume of molten metal supplied thereto will depend on the molten metal supply accuracy.

Furthermore, the molten metal supply device, in particular the members thereof that come into contact with the molten metal, must be formed from a ceramic that has superior low thermal expansion and thermal shock resistant properties. For example, in aluminum alloy casting equipment, an aluminum titanate ceramic ladle is often used as a measuring device in order to move a predetermined amount of molten aluminum alloy from a molten metal holding furnace to a molding machine. This ladle is formed from an aluminum titanate ceramic that has superior low thermal expansion and thermal shock resistant properties.

It is well known that aluminum titanate ceramic has low thermal expansion and superior thermal shock resistant properties. However, aluminum titanate ceramic only appears to possess low thermal resistance because of cracks that appear at its grain boundaries. Thus, the fact that the mechanical strength thereof is considerably weakened by these cracks at the grain boundaries is a problem.

Therefore, between several and 10 wt % of silica is generally added to the ceramic in order to both retain the low thermal expansion properties and increase the mechanical strength thereof. In this way, grain growth during the sintering process for the aluminum titanate is suppressed, and as a result, grain boundary stress generated in the post-sintering cooling process is reduced, and thus the mechanical strength of the ceramic is improved because the generation of cracks is suppressed.

However, a significant reduction in the non-wettability of the aluminum titanate ceramic ladle will occur after it has been used continuously for about 1000 times to ladle molten metal, and aluminum will remain on the inside of the ladle and its spout. As a result, it will be difficult to supply a predetermined quantity of molten metal to the forming machine, and this will cause an increase in the defect rate caused by changes in the weight of cast metal parts.

Furthermore, pieces of aluminum alloy that have been deposited and hardened on the spout of the ladle will come into contact with the casting system equipment, thus damaging the ladle itself or the ladling machine.

At present, methods such as stopping the molten metal supply ladle and mechanically stripping off the aluminum alloy that has been deposited thereon are employed after the non-wettability thereof has been reduced. In order to increase productivity, the ladle must maintain its non-wettability for at least 10,000 ladling cycles.

Because of the reasons stated above, there have been calls for a molten metal supply device that has superior molten metal supply accuracy. In particular, there have been calls for a molten metal contact member that has superior molten metal supply accuracy due to both its non-wettability with respect to molten aluminum alloy and its ability to retain this non-wettability.

SUMMARY OF THE INVENTION

The present inventors have created the following inventions as a means of solving the abovementioned problems.

The present inventors have developed a molten metal supply device that uses an electromagnetic pump and which has good supply accuracy.

In other words, the present invention is a molten metal supply device, comprising:

-   -   a molten metal transport conduit provided with an         electromagnetic pump;     -   a rotary vane that is provided inside the transport conduit and         which rotates in accordance with the movement of the molten         metal; and     -   a detector that detects the rotational frequency of the rotary         vane.

According to this device, the amount of molten metal transported by magnetic induction inside the transport conduit can be measured based upon the rotational frequency of the rotary vane that is detected by the detector. In addition, the amount of molten metal transported can also be regulated based upon the rotational frequency of the rotary vane. Because of this, the amount of molten metal supplied can be accurately controlled. In this device, it is preferred that a means for detecting the amount of molten metal inside the transport conduit be provided in the transport conduit. According to this aspect of the invention, accuracy and precision in the detection and control of the amount of molten metal transported, that are caused by changes in the amount of molten metal inside the transport conduit, can be corrected.

In addition, one aspect of the present invention also provides;

-   -   a method of manufacturing a cast metal object by supplying         molten metal using an electromagnetic pump;     -   that is provided with a rotary vane in a transport conduit that         transports molten metal to a cavity in a cast;     -   that detects the rotational frequency of the rotary vane during         the transportation of the molten metal; and     -   that controls the amount of molten metal supplied based on the         rotational frequency.

According to this method, a highly precise cast metal object can be easily obtained.

In addition, another aspect of the present invention provides,

-   -   a measuring device for a molten metal supply device that uses an         electromagnetic pump having:     -   a rotary vane that is provided in a molten metal transport         conduit and which is rotated in accordance with the movement of         molten metal; and     -   a detector that detects the rotational frequency of the rotary         vane.     -   In this measuring device, it is further preferred that a means         of detecting the amount of molten metal inside the transport         conduit be provided in the transport conduit.     -   According to this device, the amount of molten metal transported         can be measured with a high degree of accuracy.

In addition, the present inventors have studied the decrease in the non-wettability of aluminum titanate ceramic with respect to molten aluminum alloy, and have learned that silica added to aluminum titanate ceramic is reduced by Al and Mg in the molten aluminum alloy, synthesizing Si particles on the surface of the aluminum titanate ceramic and the presence of these Si particles reduces the non-wettability. Furthermore, it was learned that due to the reduction of the silica, MgO and Al₂O are produced on the surface of aluminum titanate ceramic, and moreover because of these compounds, MgAlO₄ is produced on the surface of aluminum titanate ceramic.

In other words, the present inventors have discovered that a reduction in non-wettability can be controlled or avoided, and non-wettability can be conferred and retained, by avoiding the presence or generation of Si on the surface of aluminum titanate ceramic that come into contact with the molten aluminum alloy.

Thus, according to the present invention, the following means are provided due to the aforementioned discovery.

That is, a molten aluminum alloy contact member composed of aluminum titanate ceramic having in at least the part that comes into contact with the molten aluminum alloy:

-   -   a layer containing one or more components selected from the         group consisting of Al₂O₃, MgO, and MgAl₂O₄, wherein the Si         content of the layer is less than that in the aforementioned         aluminum titanate ceramic material.

In addition, a molten aluminum alloy contact member composed of aluminum titanate ceramic having in at least the part that comes into contact with the molten aluminum alloy:

-   -   an aluminum titanate layer having an Si content that is less         than that in the aforementioned aluminum titanate ceramic         material.

In addition, a molten metal supply device comprising these contact members is provided.

The present invention provides a method of manufacturing a molten aluminum alloy contact member composed of aluminum titanate ceramic, having:

-   -   a process for forming, in at least the part of the aluminum         titanate ceramic member that comes into contact with the molten         aluminum alloy, a layer containing one or more components         selected from the group consisting of Al₂O₃, MgO, and Al₂TiO₅,         wherein the Si content of the layer is less than that in the         aforementioned aluminum titanate ceramic material; and a     -   process for synthesizing MgAl₂O₄ by causing magnesium and/or         aluminum to act upon the layer containing Al₂O₃, MgO, and/or         Al₂TiO₅.

The present invention also provides a method of manufacturing a molten aluminum alloy contact member, having:

-   -   a process for forming, in at least the part of the aluminum         titanate ceramic member at which two or more members are jointed         and which comes into contact with the molten aluminum alloy, a         layer containing one or more components selected from the group         consisting of Al₂O₃, MgO, and Al₂TiO₅, wherein the Si content of         the layer is less than that in the aforementioned aluminum         titanate ceramic material; and     -   a process for synthesizing MgAl₂O₄ by causing magnesium and/or         aluminum to act upon the layer containing Al₂O₃, MgO, and/or         Al₂TiO₅.

Furthermore, the present invention provides a method of manufacturing an aluminum alloy casting, having:

-   -   a process of synthesizing MgAl₂O₄ in a layer containing Al₂O₃,         MgO and/or Al₂TiO₅ by causing a molten aluminum alloy contact         member composed of an aluminum titanate ceramic material,         provided in at least the part that comes into contact with the         molten aluminum alloy with a layer containing one or more         components selected from the group consisting of Al₂O₃, MgO, and         Al₂TiO₅, and containing less Si than that in the aforementioned         aluminum titanate ceramic material, to come into contact with a         molten aluminum alloy containing Mg in at least part of the         casting process.

The present invention also provides a method of manufacturing a molten aluminum alloy contact member, having:

-   -   a process of synthesizing MgAl₂O₄ in a layer containing Al₂O₃,         MgO and/or Al₂TiO₅ by causing a molten aluminum alloy contact         member composed of an aluminum titanate ceramic material,         provided in at least the part that comes into contact with the         molten aluminum alloy with a layer containing one or more         components selected from the group consisting of Al₂O₃, MgO, and         Al₂TiO₅, and containing less Si than that in the aforementioned         aluminum titanate ceramic material, to come into contact with a         molten aluminum alloy containing Mg in at least part of the         casting process.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 A figure illustrating the overall construction of a molten metal supply device according to the present invention.

FIG. 2 A figure of a transport conduit and an electromagnetic pump viewed from above.

FIG. 3 Cross sectional views (a) and (b) illustrating a preferred disposition of the electromagnetic pump with respect to the transport conduit.

FIG. 4 A cross sectional diagram illustrating the entire measuring device in the molten metal supply device.

FIG. 5 A figure illustrating an example of the structure of a rotary vane.

FIG. 6 FIG. 6(a) shows a cross sectional view of the disposition of the rotary vane in the transport conduit in the direction of the molten metal flow path. FIG. 6(b) shows a cross sectional view of the disposition of the rotary vane in the transport conduit in the direction that intersects the flow path. FIG. 6(c) illustrates the disposition of the rotary vane in the transport conduit as viewed from above.

FIG. 7 A figure illustrating a means to detect the amount of molten metal in the transport conduit.

FIG. 8 A cross sectional view illustrating one example of a structure for mounting the rotary vane inside the transport conduit.

FIG. 9 A perspective view illustrating the structures of a fitting hole and a cap for mounting the rotary vane into the transport conduit.

FIG. 10 A cross sectional view illustrating one example of how the cap is fastened to the transport conduit.

FIG. 11 A figure illustrating one example of a reverse flow prevention device.

FIG. 12 A figure illustrating a method for controlling an electromagnetic pump when the transport of molten metal is initiated.

FIG. 13 FIGS. 13(a) and 13(b) illustrate the shape of a ceramic ladle produced in an embodiment. FIG. 13(a) is a plan view, and FIG. 13(b) is a cross sectional view taken along the line A-A of FIG. 13(a).

FIG. 14 FIGS. 14(a) and 14(b) illustrate the shape of a ceramic bonded set produced in an embodiment. FIG. 14(a) is a vertical cross section showing the bonded set that has been vertically separated, and FIG. 14(b) is a plan view of the lower member thereof.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Details of embodiments of the present invention will be described below.

The molten metal supply device that uses an electromagnetic pump according to the present invention is comprised of at least a rotary vane that rotates in accordance with the movement of molten metal that is transported inside a molten metal transport conduit by the electromagnetic pump, and a detector that detects the rotational frequency of the rotary vane. Said rotary vane and the detector form a measuring device according to the present invention.

In addition, the casting manufacturing method according to the present invention should preferably employ this supply device.

The molten metal supply device according to the present invention will be illustrated below, and an embodiment of the present invention will be described in detail.

The overall structure of a molten metal supply device 2 is shown in FIG. 1. The molten metal supply device of the present invention (hereinafter referred to as “the supply device”) may be a device for supplying molten metal for metal casting, or a device for supplying molten metallic sodium to a fast breeder reactor, but is preferably a molten metal supply device for metal casting.

The supply device 2 is a device for supplying molten metal for metal casting, and comprises a transport conduit 4, an electromagnetic pump 10 disposed along the conduit, and a measuring device 20.

(Transport Conduit)

The shape of the transport conduit 4 provided in the supply device 2 that transports molten metal is not particularly limited, but preferably has a flat shape. When the transport conduit 4 has a flat shape, an electromagnetic pump is efficiently formed, by disposing an inductor adjacent to the long sides of the transport conduit 4. In other words, sufficient drive torque can be obtained with respect to the molten metal even if no core is provided inside the conduit. More specifically, a flat rectangular pipe or an elliptically shaped cylinder can be employed as the transport conduit 4.

The transport conduit 4 may be made of a non-magnetic material through which magnetic flux can pass, and ceramics can be used. Preferably, a ceramic having a low thermal expansion, with the coefficient of thermal expansion being 1×10⁻⁶/° C. (room temperature to 1000 ° C.) or lower should be used. If the coefficient of thermal expansion exceeds this value, there are serious concerns that the transport conduit 4 will be destroyed by the thermal shock that occurs during the transport of the molten metal. Aluminum titanate can be used for this material. It is necessary to prevent the molten metal inside the transport conduit 4 from cooling and hardening. Because of this, it is preferred that the transport conduit 4 be insulated so that the metal therein is maintained at its melting temperature. In particular, it is preferred that the thermal conductivity of the transport conduit 4 be increased by forming concave grooves in the surface of the transport conduit 4, and that a tube-shaped heater be wrapped around the transport conduit 4.

On the other hand, the electromagnetic pump 10 disposed on the periphery of the transport conduit 4 must be cooled in order to ensure its operation. Because of this, it is preferred that an insulating layer be formed around the outer periphery of the transport conduit, which is heated and insulated. The insulating layer is preferably composed of an insulating material and a gas (air) layer. A ceramic, glass or the like can be used as the insulating material. In addition, the gas layer can be formed such that air is forced to pass through a ventilation conduit. It should be noted that it is preferred that the transport conduit 4 be insulated along its entire length.

(Electromagnetic Pump)

A variety of structures can be employed as the electromagnetic pump 10 in the supply device 2. The electromagnetic pump 10 may be either an external type or an immersion type, or may be a modified version of these.

An inductor 12 of the electromagnetic pump 10 is disposed such that it generates movement torque in the molten metal inside the transport conduit 4. The inductor 12 is comprised of at least a stator core 14 and a coil 16.

FIG. 2 shows an upper view of the transport conduit 4 and the electromagnetic pump 10.

Depending on the shape of the transport conduit 4, sufficient drive torque may be produced in the molten metal inside the transport conduit by the stator core 14 and the coil 16 only. However, it is also possible to provide a core inside the transport conduit 4 such that said core faces the stator core.

It is possible to use the stator core 14 and the coil 16 by themselves if the inductor 12 comprising the stator core 14 and the coil 16, which are provided facing each other across the transport conduit 4, does not require a separate core inside the transport conduit 4 because the transport conduit 4 is sufficiently narrow.

In addition, the inductor 12 comprising the stator core 14 and the coil 16 can be provided inside the transport conduit 4. For example, it is possible to use a type of transport conduit 4 that has a double wall structure having an outer tube and an inner tube, and to position the stator core 14 and the coil 16 inside the inner tube and form the outer tube from a magnetic material to be used as a core.

Note that the inductor 12 can be disposed in a variety of configurations with respect to the transport conduit 4, but it is preferred that it be disposed as shown in FIG. 3. In other words, when the stator core 14 and the coil 16 are disposed on the exterior of the transport conduit 4, it is preferred that they be disposed such that they are in the same horizontal position (i.e., at the same height) on two sides of the transport conduit 4 having a rectangular shape that is longer in the vertical direction, or that they be inclined from horizontal up to 15 degrees. If they exceed 15 degrees, there is a great deal of concern that elements of the electromagnetic pump 10 may be damaged, should molten metal leak from the transport conduit 4. More preferably, the inductor 12 is inclined in an angular range between the horizontal and 6 degrees from the horizontal. Note that as shown in FIGS. 3(a) and 3(b), it is preferred that the horizontal central line of the transport conduit 4 match the horizontal central line of the inductor 12 on both sides thereof when viewed from a perpendicular cross section in the axial direction of the transport conduit 4.

The supply device 2 can further be provided with a molten metal holding furnace 18 that maintains molten metal in its molten state. In this situation, it is preferred that the transport conduit 4 be arranged such that it is connected to the molten metal holding furnace 18 from near the bottom thereof and extends upward. Furthermore, in the case of a casting device, the front end of the transport conduit is connected to a cavity 5 used for metal casting.

(Measuring Device)

A measuring mechanism (device) for the molten metal transported by the electromagnetic pump 10 in the supply device 2 comprises a rotary vane 22 that rotates in accordance with the movement of the molten metal, and a detector 32 that detects the rotational frequency of the rotary vane. The detailed structure of the measuring device 20 is shown in FIG. 4.

(Rotary Vane)

One embodiment of the rotary vane 22 is shown in FIG. 5. The rotary vane 22 is formed into a shape and structure that is capable of being rotated by the molten metal that moves inside the transport conduit 4. The shape of the vane is not particularly limited, and can be a screw type or an impeller type. It is preferable that the vane be the impeller type.

In the device 2, the rotary vane 22 is formed from a shaft 24 and blades 26 arranged on the shaft 24. Pressure is applied to the blades 26 by the movement of the molten metal, and in this way the blades 26 and the shaft 24 are rotated.

It is preferred that the rotary vane 22 be formed from a material having such characteristics as non-wettability, corrosion resistance, and thermal shock resistance, with respect to the molten metal applied to the supply device 2. In particular, it is preferred that the coefficient of thermal expansion be 1×10⁻⁶/° C. (room temperature to 1000° C.) or lower if the vane 22 is to be used for molten metallic aluminum. If the coefficient of thermal expansion exceeds this value, there will be a conspicuous increase in the possibility that the rotary vane 22 will be damaged. Ceramic is a non-magnetic material that has such a coefficient of thermal expansion, and in particular, a ceramic that is composed primarily of aluminum titanate (TiAl₂O₅) or Sialon can be used. Note that Sialon is a type of solid solution of Si₃N₄, and can be one of two types: β′-Sialon and α-Sialon. β′-Sialon is a compound represented by the formula Si_(6-z)Al_(z)O_(z)N_(6-z) with z being 0 or greater up to a maximum value of 4.2. In addition, α-Sialon is a compound represented by the formula M_(x)(Si, Al)_(12(N, O)) ₁₆, with x being 0 or greater up to 2.0. M is one or more selected from the group consisting of Li, Mg, Ca, and the rare earth elements (including Y, Nd, Yb or the like).

It is preferable that the rotary vane 22 be disposed inside the transport conduit 4 such that the rotary shaft 24 is perpendicular with respect to the direction in which the molten metal moves. More preferably, the rotary shaft 24 should be vertical. This is particularly preferable in situations in which the inductor 12 is disposed on both sides of the transport conduit 4.

FIG. 6 shows the rotary vane 22 disposed inside the transport conduit 4. As shown in FIG. 6(a) and FIG. 6(b), when the rotary shaft 24 of the rotary vane 22 is perpendicular to the direction in which the molten metal flows and is disposed vertically, it is preferable that the rotary shaft 24 be disposed such that it is eccentric with respect to the vertical center of the transport conduit 4, as shown in FIG. 6(b). In other words, it is preferable that the rotary shaft 24 be disposed such that the width of the flow path of the molten metal formed between the rotary vane 22 and the sidewall of the transport conduit 4 are not uniform. When such a configuration is used, the rotation of the rotary vane 22 will be smoothly initiated and maintained because a non-uniform differential pressure will be applied to the rotary vane 22 by the movement of the molten metal. In this situation, a greater pressure will be applied to the blades 26 located on the side where the molten metal flow path is wider, and the rotary vane 22 will be rotated such that the blades 26 on said side will move in the downstream direction.

In addition, it is preferable that the inductor 12 also be disposed in the position in which the rotary vane 22 is disposed. In this situation, it is preferable that the inductor 12 be disposed such that it is on both sides of the rotary shaft 24 of the rotary vane 22, and it is more preferable that the rotary vane 22 be eccentric inside the transport conduit 4 between the inductors 12 facing each other. When disposed in this manner, the molten metal being driven by the inductors 12 will effectively rotate the rotary vane 22.

Furthermore, in order to make it easer to rotate the rotary vane 22, it may be directly driven by an external motor 40 (see FIG. 4). In this way, sufficient rotary force can be supplied to the rotary vane 22, and the rotary vane can be reliably rotated to transport the molten metal. In particular, it is preferred that the external motor 40 be used to initiate the rotation of the rotary vane 22.

(Rotational Frequency Detector)

A rotational frequency detector serves to directly or indirectly detect the rotations that are transmitted to the shaft 24 of the rotary vane 22. Any of the variety of known methods can be employed as the detection mechanism.

For example, as shown in FIG. 4, the rotational frequency detector can be a pulse generator 32 that is arranged such that when the rotation of the shaft 24 inside the transport conduit 4 is transmitted, the pulse generator 32 detects the rotation and generates a pulse. Note that by transmitting the pulses generated by the pulse generator 32 to a device equipped with a pulse counter mechanism, the rotational frequency can be easily detected.

The amount of molten metal transported when the rotary vane 22 arranged in this manner is rotated once can be calculated. However, the amount of molten metal transported can fluctuate based on differences in the structure of the device or operating conditions. Thus, it is preferable to establish the parameters that cause this fluctuation based upon actual measurements, so that the amount of molten metal being supplied can be expressed based upon these parameters during actual measurement.

Furthermore, as shown in FIG. 4, the drive force of the external motor 40 can be transmitted to the shaft 24, and the rotary vane 22 can be formed so that it is rotatively driven from the exterior thereof. In this way, sufficient rotational force can be conferred to the rotary vane.

In situations in which the rotary vane 22 is rotatively driven by the external motor 40 or the like, a rotor 34 that rotates in accordance with the rotation of the shaft 24 (preferably, a plate-shaped member), and a sensor 36 that remotely detects the rotation of the rotor 34, can be arranged on the exterior of the transport conduit 4. In this situation, by providing a rotation detection hole in the rotor 34, its rotations (frequency) can be detected by means of a photoelectric sensor 36. When this type of rotor 34 and sensor 36 are provided, an abnormality is generated in the rotation of the exterior rotor 34 when an abnormality is generated in the rotary vane 22 because the rotary vane 22 inside the transport conduit 4 and the rotor 34 are formed to be integral with each other. At this time, abnormalities in the rotary vane 22 can be detected by comparing the rotational frequency detected by the sensor 36 and the expected rotational frequency being generated by the motor. Thus, when the rotary vane 22 is driven by an external motor, the rotor 34 and the sensor 36 effectively function as a sensor for detecting any abnormality in the rotary vane 22 and/or the transport conduit 4.

Note that even if the rotary vane is not driven by the external motor 40, the rotor 34 and the sensor 36 function as a mechanism to check the rotational state of the rotary vane 22.

The rotor 34 can also serve as an insulating member. In this situation, the rotor 34 is preferably formed from a material having high thermal insulation performance and a large surface area. Furthermore, the rotor 34 can function as a more effective insulator if a nozzle 38 for a cooling means such as air or the like that is supplied from a gas supply source blows the cooling means such as air onto the rotor 34.

(Detection of the Amount of Molten Metal Inside the Transport Conduit)

When calculating the amount of molten metal transported inside the transport conduit 4 from the rotational frequency of the rotary vane 22, the amount of molten metal transported per rotation will change according to the amount of molten metal inside the transport conduit 4. A means to detect the volume of molten metal inside the transport conduit 4 is provided in order to compensate for fluctuations in the transported amount caused by the volume of the molten metal. This means is not particularly limited, but is preferably a means to detect the volume of molten metal by detecting the surface level of the molten metal inside the transport conduit 4. For example, a float that floats on the molten metal can be provided inside the transport conduit 4, and the magnitude of the displacement of this float can be detected from outside. A detection member that is linked to the displacement of the float can be provided on the float to detect the amount of fluctuation of the float from outside.

A preferred structure is illustrated in FIG. 7. FIG. 7 shows a float 28 installed on the transport conduit 4 via a mounting unit 30. In this example, the float 28 includes a catch 28 a that is caught on the upper edge of the mounting unit 30, and a contact member 28 b that comes into contact with the molten metal inside the transport conduit 4. The catch 28 a includes an indicator 29 that indicates the displacement of the float 28. The catch 28 a of the float 28 is engaged with the upper edge of the mounting unit 30 to enable the float 28 to rock, and at the same time, the mounting unit 30 has a space 30 a that can accommodate the maximum displacement of the float 28 without hindering its rocking movements. In this example, the float 28 itself serves as a detection member, and the displacement produced by the contact member 28 b is transmitted as is to the catch 28 a and the indicator 29, and thus is easily comprehended from outside. Note that it is of course possible to use a separate detection member to transmit the displacement of the float to the outside.

The displacement magnitude of the float that is transmitted to the outside can be detected by a variety of known detection means, switching means, or the like, and can be detected as the volume of molten metal. For example, the displacement magnitude of the float can be detected with a differential transformer, a magnetic sensor, or the like. Furthermore, the amount of molten metal transported that is ascertained from the rotational frequency of the rotary vane 22 can be corrected based on the volume of molten metal obtained from the sensor.

Preferably, the float, the mounting unit, and the detection member all have superior non-wettability and thermal shock resistance, and have a coefficient of thermal expansion (room temperature to 1000 degrees C.) of 1×10⁻⁶/° C. or less. More specifically, it is preferable that these members be formed primarily of aluminum titanate.

(Rotary Vane Securing Structure)

The rotary vane 22 must be disposed inside the transport conduit 4 with excellent sealing performance, and is preferably mounted such that it can easily be removed from the transport conduit 4 for maintenance or replacement. In addition, it is preferred that the rotary vane 22 be mounted such that the effects of thermal expansion can be avoided as much as possible.

Because of this, as shown in FIG. 8 and FIG. 9, it is preferred that the rotary vane 22 be snapped into the transport conduit 4, primarily using tapered concave and convex members. More specifically, a tapered fitting hole 42 is provided in the transport conduit 4 in which the caliber thereof grows smaller toward the interior of the conduit, a cap 44 is employed that has a tapered convex portion 46 that is fitted to and matches the fitting hole 42, and a through hole 48 in which the shaft 24 can be mounted is provided in the convex portion 46. In this way, the rotary vane 22 can be mounted inside the transport conduit 4 by fitting the aforementioned cap 44 into the aforementioned fitting hole 42, and thus the precision of the seal on the conduit 4 can be improved and maintained by means of a mechanical fitting.

If thermal expansion is taken into consideration, the transport conduit 4 and the cap 44 are preferably formed from a material that has a coefficient of thermal expansion of 1×10⁻⁶/° C. (room temperature to 1000° C.), and more specifically, are preferably formed primarily from aluminum titanate. In addition, it is preferable that the rotary vane also be formed from a material having a coefficient of thermal expansion of 1×10⁻⁶/° C. (room temperature to 1000° C.) or less, and preferable that this material be aluminum titanate ceramic.

Note that the means of securing the cap 44 to the transport conduit 4 is not particularly limited. The cap 44 can be secured to the transport conduit 4 by means of a thermal resistant material, e.g., a stainless steel fastener (a stainless steel band) or a screw member. For example, as shown in FIG. 10, one of the end loops of an endless stainless steel band 50 is placed on the edge of the cap 44, and the other end loop of the band 50 can be secured by latching it to a band latch unit 52 fixed at a predetermined position.

The securing member preferably has a coefficient of thermal expansion of 2×10⁻⁵/degrees C. (room temperature to 800° C.) or less, but in order to avoid the loosening of the secured state that may be caused by the thermal expansion of the securing member, it is preferred that a constant tensile force be added to the securing member. For example, in the aforementioned band latching unit 52, the securing member 50 that is latched by the latch unit 52 can be mounted such that it can be maintained in a constant-pressure fitted state that is not affected by thermal expansion. More specifically, the band latch unit 52 is disposed in a predetermined position via an elastic body 54 that expands and contracts. In this situation, the band latch unit 52 is continuously energized in the direction that the elastic body 54 attempts to return to by means of the restoring force of the elastic body 54. Here, the direction in which the band latch unit 52 is energized is the same direction that can strengthen the pressure fitting by the securing member 50. By latching the securing member 50 to the band latch unit 52, the securing member 50 is energized in a constant pressure fitting direction. As a result, even if the securing member 50 thermally expands, the effects of this are avoided and a stable pressure-fitted state can be maintained.

In addition, for example, a compressed elastic body can also be used to energize the securing member 50 in the pressure-fitting direction. In this situation, the restoring force that attempts to expand or contract the elastic body is used to energize the securing member. More specifically, the elastic body is secured in the compressed state onto the inner side of the loop of said looped securing member, the restoring force of the elastic member is resisted, and the securing member is mounted thereby. When made in this manner, even if the securing member thermally expands, the restoring force of the elastic body can compensate for the loosening of the pressure-fitted state. Note that not only a variety of shapes of coil springs can be used for the elastic body, but an elastomer can be used as well. However, the elastic body preferably has thermal resistance and low thermal expansion.

Note that this type of securing structure is particularly preferable in situations in which the shaft 24 is inserted into the transport conduit 4 from above.

Also note that the position of the rotary vane 22 can be made adjustable by a height adjustment means arranged on the portion of the shaft 24 outside of the top of the conduit 4. For example, the adjustment means may be a screw mechanism, and may be a structure formed to use interchangeable roller bearings of different heights.

Furthermore, it is preferable that the shaft 24 comprises an insulating material so that the heat of the rotary vane 22 is not transmitted outside the transport conduit 4.

(Reverse Flow Prevention Device)

A reverse flow prevention device can be provided in order to prevent the reverse flow of molten metal due to the rotation of the rotation vane 22. The reverse flow prevention device can be provided as a wall-shaped body 60 on the downstream side of the rotary vane and to the rear in the rotational direction of the rotary vane. In other words, as shown in FIG. 11, the reverse flow prevention device is on the downstream side of the rotary vane 22 at a point that corresponds to approximately ¼ of one rotation of the blades 26 in the opposite direction from the flow of the molten metal, and extends approximately along the rotation track of the tip of the blades 26. This wall-shaped body 60 prevents the molten metal held between the rotating blades 26 from moving in the reverse direction with the rotation of the rotary vane 22, and ensures that the molten metal held between the rotating blades 26 moves in its intended downstream direction.

The shape of the wall-shaped member is not particularly limited, but may be comprised of a wall that runs approximately along the rotation track of at least the tip of the blades 26.

Next, a method of using this type of molten metal supply device 2 to supply molten metal to a cavity or the like of a metal cast and manufacture a cast metal object will be described.

First, molten metal in the molten metal holding furnace 18 is supplied to a cavity for a metal cast by operating the electromagnetic pump 10. As the molten metal is transported, the rotary vane 22 provided inside the transport conduit 4 rotates, and the rotational frequency thereof is detected by the detector 32. If the relationship between the rotational frequency and the amount of molten metal has been established, the operating time of the electromagnetic pump 10 and the power supply are adjusted based on the rotational frequency, such that the desired time of rotation of the rotary vane 22 and/or the rotational frequency thereof are obtained in order to supply a predetermined amount of molten metal to the cavity. In this way, a constantly accurate amount of molten metal can be supplied to the cavity of the metal cast, and a cast metal object can be manufactured with a high degree of precision.

Furthermore, in situations in which a detection means for detecting the volume of molten metal (molten metal level) that flows inside the transport conduit 4 is provided, fluctuations in the amount of molten metal supply obtained from the rotational frequency of the rotary vane 22 (caused by the volume of molten metal (molten metal level)) are compensated for based on the detected volume of molten metal, thereby making a more accurate and precise supply volume control possible.

Note that when the driving of the electromagnetic pump 10 is initiated, it is preferable that the operation of the electromagnetic pump 10 be controlled such that pressure is applied to the rotary vane 22 by the non-uniform movement of the molten metal so that the rotary vane 22 rotates smoothly inside the transport conduit 4. In other words, it is preferable that a uniform thrust not be applied on the blades 26 arranged on the rotary vane 22 by the movement of the molten metal. More specifically, the inductors 12 disposed opposite each other with respect to the shaft 24 of the rotary vane 22 are not operated simultaneously. In particular, as shown in FIG. 12, when the shaft 24 is eccentrically disposed inside the transport conduit, the inductor 12 on the side having the large gap between the rotary vane 22 and the inner wall of the transport conduit 4 is operated first, and the rotation of the rotary vane 22 due to the operation of this inductor 12 is confirmed by the detector 32. Here, after the stable rotation of the rotary vane 22 is confirmed, for example after 10 rotations (10 pulses) or more are confirmed, the inductor 12 on the opposite side is operated next, thereby placing the electromagnetic pump 10 into normal operation. This differential system is particularly effective in situations where the thrust due to electromagnetic induction is small.

Note that each element of the present invention described above can be employed separately or in combination with the molten metal supply device, the measurement device, the method of manufacturing a cast metal object, and the casting device of the present invention.

As described above, the present invention can adopt each of the following aspects.

(1) A molten metal supply device that uses an electromagnetic pump, the molten metal supply device comprising:

-   -   a molten metal transport conduit provided with an         electromagnetic pump;     -   a rotary vane that is provided inside the transport conduit and         which rotates in accordance with the movement of the molten         metal; and     -   a detector that detects the rotational frequency of the rotary         vane;         wherein the rotation shaft of the aforementioned rotary vane is         eccentrically disposed inside the aforementioned transport         conduit.

(2) A molten metal supply device that uses an electromagnetic pump, the molten metal supply device comprising:

-   -   a molten metal transport conduit provided with an         electromagnetic pump;     -   a rotary vane that is provided inside the transport conduit and         which rotates in accordance with the movement of the molten         metal; and     -   a detector that detects the rotational frequency of the rotary         vane;         wherein the aforementioned rotary vane includes a shaft and         blades arranged on the shaft;     -   the aforementioned shaft is mounted in the transport conduit via         a cap member having a convex portion that is fitted into a         tapered fitting hole provided in the aforementioned transport         conduit and a throughhole that passes through the convex portion         and in which the shaft can be fitted.

It should be noted that, in this device, it is preferred that the shaft, the rotary vane, the transport conduit, and the cap member all be formed primarily of aluminum titanate.

(3) A molten metal supply device that uses an electromagnetic pump, the molten metal supply device comprising:

-   -   a molten metal transport conduit provided with an         electromagnetic pump;     -   a rotary vane that is provided inside the transport conduit and         which rotates in accordance with the movement of the molten         metal; and     -   a detector that detects the rotational frequency of the rotary         vane;         wherein the aforementioned cap member is pressure-fitted in the         aforementioned transport conduit by means of a securing member.

In this aspect, it is preferred that the aforementioned securing member be a low thermal expansion metal such as stainless steel.

(4) A molten metal supply device that uses an electromagnetic pump, the molten metal supply device comprising:

-   -   a molten metal transport conduit provided with an         electromagnetic pump;     -   a rotary vane that is provided inside the transport conduit and         which rotates in accordance with the movement of the molten         metal; and     -   a detector that detects the rotational frequency of the rotary         vane;         wherein the aforementioned cap member is pressure-fitted in the         transport conduit by means of a securing member; and     -   a tensile force of a degree that can compensate for the thermal         expansion of said securing member is applied to the         aforementioned securing member.

In this aspect, the tensile force is preferably applied by an elastic body such as a coil spring.

(5) A molten metal supply device that uses an electromagnetic pump, the molten metal supply device comprising:

-   -   a molten metal transport conduit provided with an         electromagnetic pump;     -   a rotary vane that is provided inside the transport conduit and         which rotates in accordance with the movement of the molten         metal; and     -   a detector that detects the rotational frequency of the rotary         vane;         wherein the aforementioned rotary vane is primarily a low         thermal expansion ceramic such as aluminum titanate or Sialon.

According to the present invention, the accuracy of the supply of molten metal can be improved in an electromagnetic pump type molten metal supply device. In addition, a metal casting device having superior molten metal supply accuracy can be provided.

Furthermore, according to the device of the present invention, a cast metal object having superior accuracy can be manufactured.

(6) A molten metal supply device that uses an electromagnetic pump according to any of the devices (1) to (5) described above, the molten metal supply device comprising:

-   -   a device to detect the volume of molten metal inside the         transport conduit.

According to this device, the supply of molten metal can be controlled with a high degree of accuracy.

(Molten Aluminum Alloy Contact Member)

Next, a molten aluminum alloy contact member will be described.

The aluminum alloy in the present invention is defined as an alloy whose primary component is aluminum. More specifically, other than aluminum, the aluminum alloy can contain at least one or more metals that can form an alloy with aluminum, such as Cu, Si, Mg, Zn, Fe, Mn, Ni, or Ti. Preferably, the alloy contains Mg. The aluminum alloy preferably contains 20 wt % or less of Mg relative to the whole.

Examples of the aluminum alloys that can be used in the present invention are illustrated in Table 1 (units: wt %) TABLE 1 Cu Si Mg Zn Fe Mn Ni Ti Al 2.0 7.0 0.5 1.0 1.0 0.5 0.3 0.2 remaining to to or or or or or or portion 4.0 10.0 less less less less less less

The molten alloy contact member of the present invention is preferably applied to a member for molten metal having a part that may come into contact with the molten metal alloy. Specific examples include a ladle, a molten metal transport conduit, and an agitator. Maintenance of these parts is made easier, and the accuracy of the handling of the molten metal is improved. It is particularly preferable that the molten alloy contact member of the present invention be applied to ladles.

In addition, the molten alloy contact member of the present invention can be preferably applied even to a member comprising an aluminum titanate ceramic bonded section, such as a conduit and molding die. The effect of increasing the non-wettability of the bonded section interface is that the intrusion of molten metal into gaps in the bonded section due to capillarity can be effectively suppressed. In this way, the maintenance of the junction is made easier.

Note that the molten alloy contact member of the present invention is preferably applied to a molten metal supply device that uses an electromagnetic pump. It is particularly preferable to apply the molten alloy contact member to the rotary vane, the blades, the shaft, the cap member, the float and the float-mounting unit of the molten metal supply device of the present invention.

The aluminum titanate ceramic that is the base material of the contact member of the present invention is a ceramic that is primarily composed of aluminum titanate (Al₂TiO₅), and contains Si. Note that the Si contained therein is typically in the form of silica (SiO₂), but is not limited to this form. Si may be in the form of a metallic element or a complex oxide of other metals. The amount of silica contained in the aluminum titanate ceramic is not particularly limited, but is normally between 1 to 10 wt % and preferably, 4 to 8 wt %. Note that the aluminum titanate ceramic may also contain Fe₂O₃, MgO, or the like.

A layer containing one or two or more compounds selected from the group consisting of Al₂O₃, MgO, and MgAl₂O₄ is provided at least at the position in which the aluminum titanate ceramic contact member comes into contact with the molten alloy. By providing this layer, the dispersion of the Si in the aluminum titanate ceramic toward the side that is in contact with the molten alloy is effectively suppressed when the contact member comes into contact with the molten aluminum alloy.

In addition, when the molten alloy contains Si, contact between that Si and the aluminum titanate ceramic can be avoided.

The layer containing one or two or more compounds selected from the group consisting of Al₂O₃, MgO, and MgAl₂O₄ can be a layer substantially formed from one of these compounds, or a layer that is substantially formed from a combination of these compounds. In either case, it is preferred that the layer be substantially formed from these compounds or consist of only these compounds. It is even more preferable that the layer be single-phase ceramic that is substantially free of other ceramics. In addition, the layer can have a laminated structure that includes a plurality of layers.

The Al₂O₃ is preferably α-Al₂O₃. An α-Al₂O₃ layer can be obtained by forming an alumina film by dip-coating with Aluminasol, and then baking this alumina film in the presence of air (preferably at 1100 to 1500° C.).

The MgO layer can be obtained by dissolving a magnesium salt in water, dip coating, and then baking the layer in the presence of air (preferably at 1100 to 1500° C.). The layer is preferably obtained using dip-coating in an aqueous solution of magnesium nitrate, and then baking it in the presence of air (preferably at 1100 to 1500° C.).

The MgAl₂O₄ layer is obtained by forming an Al₂O₃ layer and/or a MgO layer, and then applying Mg or MgO, and/or Al or Al₂O₃, to the coating film. In addition, the MgAl₂O₄ layer can also be obtained by forming the raw materials prepared to obtain MgAl₂O₄ and then baking them to produce a spinel in the layer. It is preferable that after the α-Al₂O₃ layer or the MgO layer is formed, the contact member be formed in place by immersing it in molten magnesium or a molten metal containing Mg (for example, a molten aluminum alloy) for a fixed period of time. It is most preferable that the MgAl₂O₄ layer be formed in place after the α-Al₂O₃ layer is formed.

The layer containing one or two or more compounds selected from the group consisting of Al₂O₃, MgO, and MgAl₂O₄ contains less Si than the aluminum titanate ceramic material. Preferably, the amount of Si contained therein is 3 wt % or less, and more preferably 1 wt % or less. Furthermore, it is preferable that the layer be substantially free of Si. Here, “being substantially free of Si” is defined as a Si content of 0.1 wt % or less, and more preferably 0.01 wt % or less.

The layer containing Al₂O₃, MgO, and MgAl₂O₄ preferably has one dispersion suppression function selected from amongst the three following types (1)-(3).

-   -   (1) The layer containing Al₂O₃, MgO, and MgAl₂O₄ can suppress         the diffusion of Si (other than Si, silica (SiO2) being typical)         in the aluminum titanate ceramic. More specifically, it provides         a degree of compaction and/or film thickness that can exhibit         said diffusion suppression function.

Note that the diffusion of Si in the aluminum titanate ceramic is defined as diffusion of Si out of the aluminum titanate ceramic (toward the molten metal).

-   -   (2) In addition, said layer can control the diffusion of Al and         Mg in the molten aluminum alloy toward the aluminum titanate         ceramic. More specifically, the layer provides a degree of         compaction and/or film thickness that can exhibit said diffusion         suppression function.     -   (3) When the molten aluminum alloy contains Si, the diffusion of         Si toward the aluminum titanate ceramic can be suppressed. More         specifically, the layer provides a degree of compaction and/or         film thickness that can exhibit said diffusion suppression         function.

From amongst the above, it is more preferable to have two or more types. In particular, it is preferable to have (1) and (2). In addition, (3) is preferred when the molten aluminum alloy contains Si. It is most preferable that the layer comprises all of the diffusion suppression functions.

To exhibit this type of diffusion suppression function, a film thickness of 0.1 μm to 1000 μm is preferred. When the thickness is less than 0.1 μm, the coating film will be quickly worn away due to repeated contact with the flow of molten alloy, and will basically lose its diffusion suppression function and non-wettability. In addition, when the thickness exceeds 1000 μm, the difference in the coefficient of thermal expansion between the aluminum titanate ceramic and the coating film will cause cracks and peeling in the coating film during the cooling process that occurs after the coating is baked, and thus a diffusion suppression effect cannot be exhibited. Preferably, the layer has a film thickness of 1 μm to 500 μm, and more preferably a film thickness of 10 μm to 100 μm.

In addition, from the viewpoint of a degree of compaction, the layer containing Al₂O₃, MgO, and MgAl₂O₄ preferably has a porosity of 30% or less. When the porosity exceeds 30%, the diffusion of Al, Mg, and Si in the molten aluminum alloy, and the diffusion of Si in the aluminum titanate ceramic, are difficult to suppress.

An aluminum titanate (Al₂TiO₅) layer containing less Si than the aluminum titanate ceramic material may be used as a protective layer. By forming this layer, α-Al₂O₃, MgO, and MgAl₂O₄ will be generated on the surface of the layer due to contact with the molten alloy, and a protective layer that can confer and maintain non-wettability will be produced in place.

The Si content is preferably 3 wt % or less, and more preferably 1 wt % or less; it is even more preferable that the layer be substantially free of Si.

It is preferable that the aluminum titanate layer also be formed such that it has a compaction and/or film thickness that can suppress the diffusion of Al, Mg, or Si in the molten aluminum alloy, and can suppress the diffusion of Si in the aluminum titanate ceramic. In other words, it preferably has a thickness of 0.1 to 1000 μm and more preferably 1 to 500 μm, and preferably has a porosity of 30% or less. An aluminum titanate layer being substantially free of Si means that the Si content is preferably 0.1 wt % or less, and more preferably 0.01 wt % or less. Note that it is preferable that the aluminum titanate be substantially single phase, but it may contain one or more compounds selected from the group consisting of Al₂O₃, MgO and MgAl₂O₄.

In the present invention, by providing a surface layer containing Al₂O₃, MgO and MgAl₂O₄ and/or Al₂TiO₅, regardless of the covering film used, diffusion of Si toward the surface of the aluminum titanate ceramic due to contact with the molten aluminum alloy can be suppressed, non-wettability can be maintained, and the non-wettability of the contact portion can be effectively retained by the MgAl₂O₄ that is ultimately obtained through contact with the molten aluminum alloy. Thus, non-wettability can be retained over the long term.

In addition, the MgAl₂O₄ layer that is ultimately obtained can stably retain non-wettability because the infiltration and diffusion of Si is suppressed.

Thus, when a member that provides any of these layers at the contact position with the molten aluminum alloy is employed and a cast aluminum alloy object is manufactured, a highly accurate casting can be efficiently achieved.

In addition, by forming a layer containing Al₂O₃, MgO and/or Al₂TiO₅ at predetermined positions of the contact member, and using these positions in the process of casting aluminum alloy by bringing them into contact with a molten aluminum alloy containing Mg and/or MgO to form a MgAl₂O₄ layer, the aluminum titanate ceramic member comprising a MgAl₂O₄ layer according to the present invention can be obtained. In this way, a MgAl₂O₄ layer can be easily obtained by forming only an Al₂O₃ layer, and without specifically forming a MgAl₂O₄ layer.

In addition, during the casting process, the non-wettability due to the Al₂O₃ layer and the like is retained in the beginning, and a MgAl₂O₄ layer is continuously formed in place as the contact time increases. Since this MgAl₂O₄ layer retains the non-wettability, the non-wettability lifespan of the aluminum titanate ceramic member can be efficiently extended.

[Embodiments]

Embodiment 1: Production of the Aluminum Titanate Ceramic

The aluminum titanate (Al₂TiO₅) base powder that was used was Marusu Yuuyaku's TA-2 (containing 5 wt % SiO₂) . Water and an alumina ball were added to the base powder, the weight ratio of raw material : alumina ball : water was adjusted to 1:1:0.7, and this mixture was mixed in a ball mill for 63 hours. After that, the Al₂TiO₅ slurry was passed through a sieve (200 mesh), and water was extracted therefrom with a filter press to obtain an Al₂TiO₅ press cake.

To this press cake were added suitable amounts of water, a deflocculating agent (manufactured by Chukyo Yushi, product name: D-305), a binder (manufactured by Chukyo Yushi, product name: WE-518), and the slurry density was adjusted to 2.1 to 2.3 g/cm³.

After this, this slurry was poured into a plaster mold, and after it was cast, it was dried at room temperature to obtain a green compact. Two types of green compact were produced, the ladle shape shown in FIG. 13 and the vessel shaped bonded set (2 members) that comprise the bonded portion shown in FIG. 14. As shown in FIGS. 13(a) and (b), a ladle-shaped body 102 is a hemispherical vessel comprising one sprue; and the bonded set, as shown in FIG. 14(a), is a vessel 106 consisting of 2 members vertically disposed with respect to each other, that has as shown in FIG. 14(b), a tapered inner circumferential surface 110 in the opening of the lower member 108, and an upper member 112 that is formed into an approximately annular body that comprises an outer circumferential surface 114 that fits into the inner circumferential surface 110. The two vertically arranged members 112, 108 form an integral vessel when fitted together.

Furthermore, by baking the green compacts for one hour at 1600° C. in the presence of air, an Al₂TiO₅ ceramic sintered compact was obtained.

Embodiment 2: Forming the Al₂O₃ Layer and the MgAl₂O₄ Layer

The Al₂TiO₅ ceramic sintered compacts obtained (a total of three types) were dip-coated in Aluminasol (manufactured by Nissan Chemical, product name: Aluminasol 200 or Aluminasol 520), and then dried at room temperature. After that, an α-Al₂O₃ layer having a thickness of 5 μm was formed over the entire surface of each Al₂TiO₅ ceramic sintered compact by baking each at 1100° C. for one hour in the presence of air.

After that, each compact was immersed for one hour in a molten aluminum alloy (A4C: composition shown in Table 1), 700° C.) that contains a trace amount of Mg (0.5 wt %). In this way, the α-Al₂O₃ layer on the surface of the Al₂TiO₅ ceramic reacts with the Mg in the molten A4C, and a monophase MgAl₂O₄ layer is formed on the surface of the Al₂TiO₅ ceramic. The thickness of the MgAl₂O₄ layer is the same as the 5-μm thickness of the α-Al₂O₃ layer before being immersed in the molten A4C.

Note that the presence of α-Al₂O₃ (before immersion in the molten metal) or MgAl₂O₄ (after immersion in the molten metal) on the surface of the Al₂TiO₅ ceramic sintered compacts was confirmed by X-ray diffraction analysis. In addition, the thickness of each layer was measured by energy dispersion type X-ray diffraction analysis.

Embodiment 3: Evaluation of Non-wettability

(1) Wetting Angle

The wetting angle is measured in order to evaluate the non-wettability of the Al₂TiO₅ ceramic sintered compact with respect to the molten aluminum alloy (A4C).

The following three types of Al₂TiO₅ ceramic test pieces were used. In other words, i) a test piece in which the surface of the sintered compact produced in Embodiment 1 was cut into a 25 mm×25 mm×6 mm piece, surface-finished to 25 mm×25 mm (thickness of 5 mm) by means of a #800 diamond grindstone, and had a surface roughness (center line average roughness) of approximately 3 μm; ii) a test piece with the same surface finish, on whose surface an α-Al₂O₃ layer having a thickness of 5 μm was formed according to Embodiment 2; and iii) a test piece obtained by immersing an Al₂TiO₅ ceramic sintered body on which an α-Al₂O₃ layer had been formed in a molten aluminum alloy (A4C, 720 degrees C.) for 50 hours in order to change the surface of the α-Al₂O₃ layer to an MgAl₂O₄ layer.

An MH-type guided interlock observation device produced by Union Optical was used to measure the wetting angle. The aforementioned test pieces were placed on the device's heater with their final processed surfaces (25 mm×25 mm surfaces) facing upward, and then cylindrical pieces of aluminum alloy (A4C) that were 10 mm in diameter and 10 mm in length were placed on these surfaces. After that, the temperature was raised 5° C./min from room temperature to 700° C. in an argon gas atmosphere (flow volume 2500 cc/min), and was maintained at that point for 30 seconds. After that, at 700° C., a lamp light was radiated onto the aluminum alloy and test pieces, the images produced were projected onto a screen, and the contact angle between the surface of each test piece and the aluminum alloy was measured from these images.

The wetting angle at 700° C. was as noted below. The Al₂TiO₅ sintered compact=120 degrees, the α-Al₂O₃ coated Al₂TiO₅ sintered compact=135 degrees, and the MgAl₂O₄ coated Al₂TiO₅ sintered compact=128 degrees; thus, it is clear that the non-wettability of the Al₂TiO₅ sintered compact with respect to the aluminum alloy increases due to the α-Al₂O₃ coating and the MgAl₂O₄ coating.

(2) Non-wettability Lifespan

Two kg of 700° C. molten aluminum alloy (A4C) was poured into a ladle-shaped Al2TiOO5 ceramic sintered compact (comprising an α-Al₂O₃ layer), and after holding it there for 50 seconds, the molten metal inside the ladle was discharged. This process was repeated until the molten metal stuck to the inner wall of the ladle and remained there, even after the molten metal had been discharged. The results were that the ladle produced in the embodiment had absolutely no molten metal stuck thereto after 12,000 repetitions of this process. Because of this, it is clear that this ladle possesses and can retain excellent non-wettability. In addition, the presence of the MgAl₂O₄ layer on the inner wall of the ladle was confirmed after 12,000 repetitions of the process.

In contrast, subjecting an Al₂TiO₅ ceramic ladle not having an Al₂O₃ layer formed thereon resulted in molten metal sticking thereto after 2000 repetitions of the aforementioned process.

(3) Sealing Characteristics of a Bonded Body Comprising Bonded Sections

Each member of the Al₂TiO₅ ceramic bonded set having an α-Al₂O₃ layer thereon was fitted together at the bonding positions to form a bonded body, and the outer circumference of the bonding position was secured with a stainless steel band (width 20 mm) via an alumina fiber sheet (manufactured by Mitsui Mining Materials, product name: Almax). A piece of aluminum alloy (A4C) was placed inside the bonded body, and then its temperature was raised (20° C./min) in an argon gas atmosphere (flow volume 100 cc/min) until the temperature reached 720° C. and the aluminum alloy melted. After melting, the temperature was maintained at 720° C. for one hour, and then the temperature was reduced (20° C./min). This process was repeated 50 times.

The result of this was that absolutely no molten metal was observed leaking from the bonded position while the process was being repeated. In addition, absolutely no molten metal stuck to the molten metal contact positions on the inner wall of the bonded body, thus confirming that the bonded body retained excellent non-wettability. Note that the formation of an MgAl₂O₄ layer on the surface of the molten metal contact portions inside the bonded body was confirmed.

According to the present invention, conferring and retaining the non-wettability of aluminum titanate ceramic with respect to molten aluminum alloy can be easily achieved. 

1. A molten aluminum alloy supply device comprising: an electromagnetic pump and a molten metal transport conduit provided with said electromagnetic pump, wherein the transport conduit compises aluminum titanate ceramic base material and has in at least a part that come into contact with the molten aluminum alloy a layer which Si content is less than that in said aluminum titanate ceramic base material.
 2. A supply device as in claim 1, wherein said layer contains one or more components selected from the group consisting of Al₂O₃, MgO and MgAl₂O₄.
 3. A supply device as in claim 1, wherein said Si content of the layer is equal to or less than 3 wt %.
 4. A supply device as in claim 1, wherein said aluminum titanate ceramic base material contains α-Al2O3.
 5. A supply device as in claim 1 comprising: a rotary vane that is provided inside the transport conduit and which rotates in accordance with the movement of the molten aluminum alloy and a detector that detects the rotational frequency of the rotary vane.
 6. A supply device as in claim 5, wherein said rotary vane has a shaft and blades arranged on the shaft; the shaft is mounted in the transport conduit via a cap member having a convex portion that is fitted into a tapered fitting hole provided in the said transport conduit and a throughhole that passes through the convex portion and in which the shaft can be fitted.
 7. A supply device as in claim 6, wherein said cap member is pressure-fitted in said transport conduit by means of securing member.
 8. A supply device as in claim 7, wherein the tensile force sufficient to compensate for the thermal expansion of said securing member is applied to the said securing member.
 9. A supply device as in claim 1, wherein said transport conduit has a device detecting the volume of the molten aluminum alloy inside the transport conduit.
 10. A supply device as in claim 5, wherein said rotary vane compises aluminum titanate ceramic base material and has in at least a part that come into contact with the molten aluminum alloy a layer which Si content is less than that in said aluminum titanate ceramic base material.
 11. A casting device comprising a molten aluminum alloy supply devise as in claim
 1. 12. A molten aluminum alloy contact member, the contact member comprising aluminum titanate ceramic base material and having in at least a part that comes into contact with the molten aluminum alloy a layer which Si content is less than that in said aluminum titanate ceramic base material.
 13. A contact member as in claim 12, wherein said layer contains one or more components selected from the group consisting of Al₂O₃, MgO and MgAl₂O₄.
 14. A contact member as in claim 12, wherein said layer contains Al₂TiO₅.
 15. A contact member as in claim 12, wherein said Si content of the layer is equal to or less than 3 wt %.
 16. A contact member as in claim 12, wherein said contact member comprises one or more members selected from the group consisting of ladle, transport conduit and mixing device.
 17. A casting device comprising on or more molten aluminum titanate alloy contact member as in claim
 12. 18. A method of manufacturing aluminum alloy cast, using the molten aluminum alloy contact member as in claim
 12. 19. A method of manufacturing a molten aluminum alloy contact member comprising steps: preparing a contact member comprising aluminum titanate ceramic base material having in at least a part of the contact member a layer containing one or more components selected from the group consisting of Al₂O₃, MgO and Al₂TiO₅, wherein the Si content of the layer is less than that in the aluminum titanate ceramic base material; and synthesizing MgAl₂O₄ in the layer by causing magnesium and/or aluminum to act upon the layer.
 20. A method of manufacturing a molten aluminum alloy contact member comprising steps: preparing a contact member comprising aluminum titanate ceramic base material having in at least a part of the contact member a layer containing one or more components selected from the group consisting of Al₂O₃, MgO and Al₂TiO₅, wherein the Si content of the layer is less than that in the aluminum titanate ceramic base material; and contacting the layer of the contact member to a molten aluminum alloy containing magnesium in at least a part of molten aluminum alloy casting process and thereby synthesizing MgAl₂O₄ in the layer.
 21. A method of manufacturing an aluminium alloy cast comprising steps: preparing a contact member comprising aluminum titanate ceramic base material having in at least a part of the contact member a layer containing one or more components selected from the group consisting of Al₂O₃, MgO and Al₂TiO₅, wherein the Si content of the layer is less than that in the aluminum titanate ceramic base material; and contacting the layer of the contact member to a molten aluminum alloy containing magnesium in at least a part of molten aluminum alloy casting process and thereby synthesizing MgAl₂O₄ in the layer. 